It is known to design hard disk drives as an arrangement of subparts or subsystems. Commonly assigned U.S. Pat. No. 4,396,959 (which later became U.S. Pat. Re. No. 32,075) describes an eight inch hard disk drive having four disks and a data storage capacity of up to 40 megabytes of data with four data storage disks. Since the development of disk drives in accordance with the referenced '959 patent, disk data storage capacities have increased to the present time, wherein it is now possible to store as much as 150 megabytes on a single three and one half inch diameter data storage disk. While twelve years ago the eight inch diameter disk drive was a prevalent form factor, today the prevalent form factor is three and one half inches, and as many as eight or more three and one half inch disk drives or more may fit into the space originally required by the eight inch disk drive form factor.
As drives have become smaller, they have also become less costly per byte of storage provided. One reason that costs have been reduced is through widespread use of robotic assisted assembly of subassemblies into the completed disk drive assembly.
Disk drives are typically assembled in a very clean environment which is free of particulate contamination. Usually, assembly occurs in a Class 100 or better clean room. Once the disk stack and actuator assembly are installed, the head and disk assembly is enclosed in a sealed arrangement by installation of a gasket and cover structure. Thereafter, certain electrical procedures, such as track and servo formatting, and burn-in occur, prior to packaging for shipment to the user, etc. In some situations, it is highly desirable to perform disk formatting procedures, and burn in before installation of a main printed circuit board carrying the circuitry needed to complete the disk drive. One example of a disk drive having a capability for track formatting and burn in before installation of a main printed circuit board is found in the present assignee's prior Q2000 eight inch disk drive product series, and as also explained in commonly assigned U.S. Pat. No. 4,396,959 (later U.S. Pat. Re. No. Re32,075). The Q2000 included a main printed circuit board which was mounted adjacent to a drive cover structure. A small circuit board carrying circuitry relating to the data transducer heads and to a head positioner servo loop was mounted inside the space enclosed by the cover, and included a connector array extending through the cover. A seal was provided between the connector array and the cover, so that particulate contaminants could not enter the enclosed space.
A similar arrangement was provided in the assignee's Q500 product series, and as described in commonly assigned U.S. Pat. No. 4,639,798, and particularly FIG. 1 thereof, which illustrates the interior circuit board as having an edge connector portion extending through a slot in the base wall of the drive housing. In the Q500 product series, the main printed circuit board was mounted below the bottom wall of the base casting, rather than above the cover structure.
A slightly different approach was followed in the assignee's Q200 product series, and as described in commonly assigned U.S. Pat. No. 4,669,004, for example. In the Q200, a read preamplifier/write driver circuit 36 was mounted on a flexible plastic printed circuit substrate 38 ("flex circuit") which included an arcuate portion 42 leading to the rotary actuator structure. A connector portion 40 of the flex circuit 38 extended exteriorly from the interior of the head and disk assembly via a gap between the cover and the base casting. The flex circuit extension plugged into a receptacle on the main printed circuit board which was mounted opposite to a floor wall of the base casting. The referenced '004 patent also describes a servo writer apparatus which was used to format the data tracks by using the voice coil rotary actuator structure of the disk drive itself.
Finally, a recent U.S. Pat. No. 4,965,684 has asserted novelty in providing a connector array between a flex circuit within an enclosed head and disk assembly, and an externally mounted main printed circuit board. In addition, it was known in the prior art to provide multiple stacked and interconnected printed circuit boards in hard disk drives. In some embodiments of prior art drives, one circuit board included analog read/write electronics, while another included digital control and interface electronics.
While all of these examples of prior approaches provided effective connections from the flex circuit to external circuitry, none of them provided a space efficient, fully nested multiple printed circuit board arrangement with interconnections being carried out by a single connector pin array extending from the flex circuit, through a nested circuit board to an overlying main circuit board.